The first major of the season extends its prevailing tumbling of star players and dramatic ousting of reigning champions. On Tuesday, three-time reigning champion Novak Djokovic was knocked out the tournament by Stanislas Wawrinka in five-set thriller.

In the fourth round, the dominant Serena Williams and Maria Sharapova also suffered early exits.

Fifth-seeded Radwanska ended a streak of three consecutive quarterfinal defeats at the Australian Open with a stunning display of versatile shot-making that confused the big-hitting defending champion.

"That's the best quarterfinal I've ever played here," said Radwanska.

"I said to myself one day I have to take another step and get to the semifinal and I'm so happy I did that.

"I had to play my best tennis or even better, to be very aggressive and go for every shot I could."

Radwanska played a great game to break Azarenka's serve to open the deciding set before marching away to claim victory in a match lasting exactly two hours.

It was the first time Azarenka had been "bagelled" in a set at Melbourne Park.

"I really enjoyed my time on the court. That' what I want to do," said the Polish.

"If I put pressure on myself I play nervous and that's not what I want to do."

She next plays No. 20 Dominika Cibulkova, who won the last eight games in a one-hour, 6-3, 6-0 quarterfinal rout of No. 11-seeded Simona Halep.

The only previous occasion that the Slovakian had reached the last four at a major was at the 2009 French Open. "I was playing agressive and I was playing freely," said Cibulkova.

Azarenka's loss leaves 2011 French Open champion Li Na as the only major winner remaining in the women's draw.

Li will play 19-year-old Canadian Eugenie Bouchard in the other semifinal.